Antennas exhibit a specific radiation pattern. The overall radiation pattern changes when several antenna elements are combined in an array. Side lobes are the lobes of the far field radiation pattern that are not the main beam. The number of side lobes increase with the number of elements. Most antennas generally have side lobes. For discrete aperture antennas, for example phased arrays, the aliasing effect causes some side lobes to become substantially larger in amplitude and approach the level of the main lobe with increasing scans. These side lobes are referred to as grating lobes, which are special cases of side lobes. These grating lobes follow the envelope element pattern when the antenna is scanned. Phased arrays may be restricted by grating lobes, which cause spatial interference and scan loss. In general, for antennas used as receivers, side lobes make the antenna more vulnerable to noise from nuisance signals coming far away from the transmit source. For transmit antennas communicating classified information, side lobes represent security vulnerability, as an unintended receiver may pick up the classified information or may simply cause interference in other receivers.